Received path delay mechanism

ABSTRACT

A reception device comprising: at least one receiver and a corresponding delay buffer configured to receive portions of data for at least one data stream; wherein based on a request to switch from decoding delayed data portions retrieved from a host device from a first time point to decoding delayed data portions from a different, second time point, the request received while the controller is configured to receive the delayed data portion from said first time point for decoding; the controller is configured to;
         (a) identify one or more second-time-point delayed data portions to request from the host device;   (b) request the one or more identified second-time-point delayed data portions; and   (c) while one or both of requesting and receiving the one or more second-time-point delayed data portions, requesting one or more delayed data portions corresponding to the first time.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority under 35 U.S.C. § 119 of European Patent application no. 17173793.5, filed on 31 May 2017, the contents of which are incorporated by reference herein.

FIELD

This disclosure relates to the reception and processing of broadcast data in a multiple source receiver and in particular but not exclusively to a storage mechanism for the broadcast data.

BACKGROUND

Some modern broadcast receiver devices are designed to support multiple audio inputs from different broadcast domains. For example end user content (such as a radio show) may be received via audio streams from domains such as frequency modulation broadcasting (FM), digital audio broadcasting (DAB) and/or Internet radio. The transmit paths of these audio stream may have varying processing delays which result in streams that are misaligned in time. Initial processing at the receiver may misalign the audio streams further.

It may be a requirement for the broadcast receiver to switch from one audio stream or input to another, for example an input may be lost when the receiver moves out of range of the input's source. Due to the misalignment, the transition may not be seamless which degrades user experience. For example when switching from a transmit path with a short processing delay to a transmit path with a long processing delay, data may not yet be available on the high processing delay path. A potential approach to address this is the buffering of the received audio streams in order to realign the incoming data. However such storing may be subject to restrictions.

Embodiments of the present application may be concerned with a storage mechanism for broadcast data received at a multi-source receiver.

In a first aspect of the disclosure we provide a reception device comprising:

-   -   at least one receiver and a corresponding delay buffer         configured to receive portions of data for at least one data         stream;     -   the at least one delay buffer comprising at least part of a host         device and configured to store the portions of data received by         a respective receiver; and     -   a memory configured to maintain indexing information for the or         each of the delay buffers, the indexing information providing at         least an indication of time points in the content of each of the         portions of data; and     -   a controller configured to request delayed data portions from         one or more of the at least one delay buffer of the host device         for decoding of the delayed data portions;     -   the reception device configured such that each delayed data         portion received by the reception device from the host device in         response to each request of the controller is received as a         plurality of consecutively received sub-portions, each         sub-portion comprising a subset of the content of the delayed         data portion, the receipt of each sub-portion taking at least a         predetermined transfer time and each delayed data portion         configured such that all of its constituent sub-portions are         required for decoding said delayed data portion;     -   wherein based on a request to switch from decoding delayed data         portions from a first time point to decoding delayed data         portions from a different, second time point, the request         received while the controller is configured to receive the         delayed data portion from said first time point for decoding;     -   the controller is configured to perform the following;     -   (a) identify one or more second-time-point delayed data portions         to request from the host device based on the second time point         and the indexing information;     -   (b) request the one or more identified second-time-point delayed         data portions from the host device; and     -   (c) while one or both of requesting and receiving the one or         more second-time-point delayed data portions, request one or         more delayed data portions corresponding to the first time or at         least corresponding to a time subsequent thereto for decoding         for at least some of a total transfer time for receiving the one         or more second-time-point delayed data portions, the total         transfer time comprising the sum of the predetermined transfer         times for each sub-portion of the one or more identified         second-time-point delayed data portions.

In one or more examples, the reception device comprises a plurality of receivers and corresponding, associated delay buffers configured to receive portions of data for a plurality of data streams carrying respective content, wherein the content of each data stream is misaligned with at least one other data stream with respect to time.

In one or more embodiments, the controller is configured to determine the total transfer time for receiving the one or more identified second-time-point delayed data portions using meta information indicative of the number of sub-portions required to receive the one or more identified delayed data portions, and

-   -   based on the determined total transfer time, determine the one         or more requests, required in step (b), of the one or more         delayed data portions corresponding to the first time or times         consecutively subsequent thereto in order to continue decoding         said delayed data portions while the one or more identified         second-time-point delayed data portions are received from the         host device.

In one or more embodiments, the controller is configured to determine the total transfer time for receiving the one or more identified second-time-point delayed data portions using meta information indicative of the number of sub-portions required to receive the one or more identified delayed data portions, and

-   -   based on the determined total transfer time, a switch time         comprising the time the controller provides for switching from         decoding the delayed data portions associated with the first         time to from decoding the second-time-point delayed data         portions.

In one or more embodiments, the content of the data portions comprises one or both of audio and video for presentation to a user when decoded and the continued decoding of the one or more delayed data portions requested during the one or both of requesting and receiving of the one or more identified second-time-point delayed data portions provides for gapless presentation of the audio or video to the user.

In one or more embodiments, step (a) includes the identification of a first candidate delayed data portion comprising the delayed data portion 901 directly subsequent to the delayed data portion 900 containing the second time point 806, determination of the total transfer time of the first candidate delayed data portion and wherein:

-   -   if the total transfer time of the first candidate delayed data         portion 901 is less than the time between the second time point         806 and a time point (805 as positioned in FIG. 10) defined by         the start of the content of the first candidate delayed data         portion, the controller is caused to identify said first         candidate delayed data portion as the second-time-point delayed         data portion; and     -   if the total transfer time of the first candidate delayed data         portion 901 is greater than the time between the second time         point 806 and the time point (805 as positioned in FIG. 10)         defined by the start of the content of the first candidate         delayed data portion, the controller is caused to identify a         delayed data portion received subsequent to (i.e. 1004) the         first candidate delayed data portion as the second-time-point         delayed data portion.

In one or more embodiments, the reception device includes a first buffer and a second buffer for receiving delayed data portions from the host device;

-   -   the first buffer configured to receive the one or more delayed         data portions corresponding to the first time or at least         corresponding to a time subsequent thereto; and     -   the second buffer configured to receive the one or more         identified second-time-point delayed data portions;     -   the controller configured to provide the one or more delayed         data portions of the first buffer to a decoder while the second         buffer receives at least all of the sub-portions of one of the         one or more of the identified second-time-point delayed data         portions.

In one or more embodiments, the reception device includes a decoder configured to decode the delayed data portions received from the host device, the decoder configured to provide decoded delayed data portions for presentation to a user.

In one or more embodiments, the reception device includes a decoder-out buffer configured to hold decoded delayed data portions for presentation to a user by a content renderer.

In one or more embodiments, the reception device includes a content renderer configured to receive a decoded data stream formed of the decoded delayed data portions held in said decoder-out buffer for presentation to a user.

In one or more embodiments, each request by the controller for delayed data portions from the host device comprise a request for delayed data portions from all of the delay buffers.

In one or more embodiments, the indexing information comprises read and write pointers for each delay buffer.

In one or more embodiments, the at least one receiver is configured to receive a data stream selected from a frequency modulated FM stream, a Digital Audio Broadcast DAB stream, a Digital Audio Broadcast DAB+ stream, a T-DMB stream, an analogue audio or video stream and a digital audio or video stream.

In a second aspect of the disclosure we provide a method for a reception device comprising at least one receiver and a corresponding delay buffer configured to receive portions of data for at least one data stream; the delay buffers comprising at least part of a host device and configured to store the portions of data received by a respective receiver; and a memory configured to maintain indexing information for the or each of the delay buffers, the indexing information providing at least an indication of time points in the content of each of the portions of data; and a controller configured to request delayed data portions from one or more of the at least one delay buffer of the host device for decoding of the delayed data portions; the reception device configured such that each delayed data portion received by the reception device from the host device in response to each request of the controller is received as a plurality of consecutively received sub-portions, each sub-portion comprising a subset of the content of the delayed data portion, the receipt of each sub-portion taking at least a predetermined transfer time and each delayed data portion configured such that all of its constituent sub-portions are required for decoding said delayed data portion;

-   -   wherein based on a request to switch from decoding delayed data         portions from a first time point to decoding delayed data         portions from a different, second time point, the request         received while the controller is configured to receive the         delayed data portion from said first time point for decoding;     -   the controller is configured to perform the method of;     -   (a) identifying one or more second-time-point delayed data         portions to request from the host device based on the second         time point and the indexing information;     -   (b) requesting the one or more identified second-time-point         delayed data portions from the host device; and     -   (c) while one or both of requesting and receiving the one or         more second-time-point delayed data portions, requesting one or         more delayed data portions corresponding to the first time or at         least corresponding to a time subsequent thereto for decoding         for at least some of a total transfer time for receiving the one         or more second-time-point delayed data portions, the total         transfer time comprising the sum of the predetermined transfer         times for each sub-portion of the one or more identified         second-time-point delayed data portions.

In a third aspect of the disclosure we provide a presentation device for presentation of one or more of video and audio content to a user, the presentation device comprising the reception device of the first aspect and a host device for buffering data streams received by the reception device.

In a fourth aspect of the disclosure we provide host device for buffering data streams for a multi-source receiver comprising:

-   -   an input configured to receive portions of data from a reception         device in a forwarding message, the portions of data forming         part of at least one data stream, the input further configured         to receive indexing information associated with at least one         delay buffer in the forwarding message;     -   at least one delay buffer configured to store the respective         portions of data in the at least one delay buffer in dependence         on the indexing information;     -   the host device configured such that each delayed data portion         transferred to the reception device from the host device in         response to each request of a controller of the reception device         is transferred as a plurality of consecutively transferred         sub-portions, each sub-portion comprising a subset of the         content of the delayed data portion, the transfer of each         sub-portion taking at least a predetermined transfer time and         each delayed data portion configured such that all of its         constituent sub-portions are required for decoding said delayed         data portion at the reception device; and     -   while transferring the sub-portions of one or more         second-time-point delayed data portions to the reception device,         transferring one or more delayed data portions corresponding to         a first, different time or at least corresponding to a time         subsequent thereto for decoding by the reception device for at         least some of a total transfer time for transferring the one or         more second-time-point delayed data portions, the total transfer         time comprising the sum of the predetermined transfer times for         each sub-portion of the one or more identified second-time-point         delayed data portions.

We also disclose a reception device comprising: a plurality of receivers and associated delay buffers configured to receive portions of data for a plurality of data streams carrying respective content, wherein the content of each data stream is misaligned with at least one other data stream with respect to time; a controller configured to forward the portions of data to a host device to be stored in respective delay buffers; and a memory, which together with the controller, maintains indexing information for each of the delay buffers; wherein the controller is further configured to forward indexing information for each of the delay buffers with the portions of data.

The indexing information may comprise read and write pointers for each delay buffer. The controller may be configured to maintain the indexing information by adjusting the read pointers to point to portions in the respective delay buffers carrying corresponding content. The controller may be configured to send a forwarding message to the host device comprising the portions of data and the write pointers. The controller may be further configured to send a request message to the host device for at least one of the stored data portions, the request message comprising an associated read pointer. The controller may be further configured to send the forwarding message and the request message as part of a first communication message.

The reception device may be further configured to receive delayed data portions from the host device, wherein the received delayed data portions carry corresponding content. The reception device may be further configured to render at least one of the received delayed data portions to an output. A portion of data may have a predetermined size. The controller may be further configured to forward the portions of data in response to one portion of data being received on each of the plurality of data streams. The controller may be further configured to forward the portions of data to the host device periodically.

The reception device may be further configured to receive at least one stored portion of data from the host device in response to a request. The reception device may be further configured to receive a data portion from a further data stream received at the host device in response to a request for a data portions of at least one of the plurality of data streams. The controller may be further configured to store meta information associated with respective data portions. The meta information may comprise quality information of the respective data portion.

The controller may be further configured to identify data portions stored at the host device to be requested in dependence on at least the stored meta information. The reception device may be further configured to request the identified data portions. The reception device may be further configured to identify at least one data portion of sufficient quality to be rendered.

We also disclose a host device for buffering data streams for a multi-source receiver comprising: an input configured to receive portions of data from a reception device in a forwarding message, the portions of data forming part of a plurality of data streams carrying respective content, wherein the content of each data stream is misaligned with at least one other data stream with respect to time, the input further configured to receive indexing information associated with a plurality of delay buffers in the forwarding message; and a plurality of delay buffers configured to store the portions of data in the respective delay buffers in dependence on the indexing information.

The indexing information may comprise at least a write pointer for each delay buffer. The input may be further configured to receive a request message requesting at least one data portion from the delay buffers, the request message comprising indexing information identifying the data portions requested. The indexing information in the request message may comprise a read pointer associated with the requested data portion(s). The forwarding message and the request message may form a first communication message.

The host device may further comprise an output configured to provide data portions from the delay buffers to the reception device, the provided data portions carry corresponding content. A portion of data may have a predetermined size. The host device may further comprise an output configured to provide at least one stored portion of data from the delay buffers in response to a request from the reception device. The input may be further configured to receive a further portion of data from a further data stream, the further data stream being received from a further source and carrying the corresponding content. The output may be further configured to provide the further portion of data to a reception device in response to a request for at least one data portion from the delay buffers.

FIGURES

Embodiments will be described, by way of example only, with reference to the drawings, in which:

FIG. 1 is a schematic diagram showing an example of a multi-source receiver;

FIG. 2 is a schematic diagram showing an example of a multi-source receiver according to an embodiment;

FIG. 3 is an example flow diagram depicting the forwarding and receiving of delayed data portions to the host device;

FIG. 4 is a schematic diagram showing a further example of a multi-source receiver; and

FIG. 5 is a schematic diagram showing aspects of a multi-source receiver according to a further embodiment;

FIG. 6 shows an example arrangement of delayed data portions in a buffer for different data stream standards;

FIG. 7 shows one of the delay buffers of the host device and buffers of reception device to illustrate an example operation of the controller in accordance with an example embodiment of the disclosure;

FIG. 8 shows a view similar to FIG. 7 illustrating retrieval of delayed data portions from the host device without use of the example controller described herein;

FIGS. 9-21 show views similar to FIG. 7 over time illustrating retrieval of delayed data portions from the host device by use of a controller in accordance with an example embodiment of the disclosure; and

FIG. 22 shows an example flow diagram depicting the receiving of second time point delayed data portions from the host device.

It will be appreciated that for features that span more than one drawing like reference numerals indicate the like feature.

DETAILED DESCRIPTION

The following embodiments may be described with reference to packet streams carrying audio data. This has been done for ease of explanation only and it will be appreciated that at least some embodiments may be applicable to other types of broadcast or streaming data, for example video data. It will be appreciated that here the term broadcast is intended to cover packet streams broadcast from one entity to multiple other entities as well as packet stream broadcast from one entity to a specific few or a particular one other entity. For example, the broadcast packet stream may be a unicast stream.

In multi-source transceiver systems, content may be transmitted via a plurality of paths corresponding to different transmission technologies. The content may be commonly generated at a common data source but may be processed and transmitted via different transmit paths. Examples of such transmit technologies may include frequency modulation (FM), digital audio broadcasting (DAB), internet broadcasting and/or others. A multi-source receiving device may be able to receive transmissions of the content along two or more of these paths however, due to processing delays of the respective paths, the commonly generated content carried on the transmission paths may become misaligned.

The receiving device may rely on the content from a first transmission path to be rendered and provided to a user. If the first transmission path becomes unavailable, the receiving device may switch to provide the content from the second transmission path instead. For example, a user may be listening to the content received via an FM transmission while driving, when they drive into a tunnel and lose their FM signal. The receiving device may then switch to a second transmission, for example a DAB transmission path, to continue to provide the content to the user. Due to the differences in a processing time on the first and second paths, the content received and the first path and the content received on the second path may be misaligned. In order for the switch between the first and second path to be less noticeable, the content on the respective paths needs to be aligned. The receiving device may do this by delaying the content from the path that is ahead in time until at least a portion of the content has been received from the first and second paths. The receiving device can introduce this delay by buffering the received data from the first and second paths.

FIG. 1 is an example of such a multi-source transceiver system.

FIG. 1 shows an example of a multi-source broadcast system 100 comprising a receiving device 110 and a transmitting device 120. The transmitting device 120 comprises a common data source 121 and three transmit paths 122, 123 and 124. The common data source 121 may generate content to be transmitted via respective paths 122, 123 and 124. Each transmit path comprises a transmitter 122 a, 123 a and 124 a and a processing delay 122 b, 123 b and 124 b associated with that path.

Each of the transmit paths 122, 123 and 124 may transmit the content according to a different transmission technology. For example the first path 122 may transmit the content based on an analogue technology such as frequency modulation (FM); the second path 123 may transmit the content according to a digital transmit technology such as digital audio broadcasting (DAB); and the third transmit path 124 may transmit the content according to an additional FM or DAB path or other technology. It will be appreciated that this is by way of example only and the paths are not limited to such technologies.

Each of the three transmit technologies may be associated with a delay that is caused by the different processing that the content undergoes before it can be transmitted by the respective transmitters 122 a, 123 a and 124 a. For example, the processing on the first path 122 may cause the content to experience a first delay 122 b, the processing on the second path 123 may cause the content to experience a second delay 123 b and the processing on the third path 124 may cause the content to experience a third delay 124 b. In the above examples, the paths have been exemplified as being FM, DAB and internet broadcast. Accordingly, the first delay 122 b associated with FM is relatively short, for example a time A (depicted as one delay block). The second delay 123 b associated with DAB is longer, for example a time B (depicted as seven delay blocks). The third delay 124 b, associated with internet broadcast, may experience the longest delays, for example a time period C (depicted with eleven delay blocks).

It will be appreciated that the number of delay blocks is by way of example only and function to indicate the differing delays experienced by content generated by a common data source 121 along each path. Accordingly, corresponding content on each path reaches the respective transmitter 122 a, 123 a and 124 a at differing times and the content along the three paths is misaligned with respect to time. For example, the content on the second path 123 may be misaligned by a time (B-A) with respect to the content on the first path 122. The content on the third path 124 may be misaligned by a time (C-A) with respect to the content on the first path 122 and by a time (C-B) with respect to the content on the second path 123.

The receiving device 110 comprises three receive paths 132, 133 and 134, each comprising a respective receiver 132 a, 133 a, 134 a and delay buffer 141, 142 and 143. Data streams comprising the content received on each of the paths 132, 133 and 134 is stored in the respective delay buffer 141, 142 and 143 for that path. An output of the delay buffers is coupled to an output 111 via a selection mechanism 112. The output 111 provides data from a selected delay buffer to be rendered and to provide to a user, for example via a speaker. The rendering may include decoding and further processing to output the content.

In this example, each of the receiver paths 132, 133 and 134 are configured to receive a data stream comprising the commonly generated content and being transmitted according to a different transmission technology. For example, the first receive path 132 may be configured to receive the content transmitted in accordance with FM; the second receive path 133 may be configured to receive the content transmitted in accordance with DAB; and the third receive path 134 may be configured to receive the content transmitted in accordance with internet broadcast.

For example, the first receive path 132 may be configured to receive the content transmitted from the first transmit path 122; the second receive path 133 may be configured to receive the content transmitted from the second transmit path 123; and the third receive path 134 may be configured to receive the user content transmitted from the third transmit path 124.

The respective receivers 132 a, 133 a and 134 a receive respective data streams comprising the content. The content in the data streams may be misaligned due, at least in part, to the delays A, B and C introduced by the relative processing paths 122, 123 and 124.

In this example, in order to realign the content, the receiving device 110 may delay or buffer the respective data streams until at least a portion of the user content has been received on all the packet streams. In general, the delay buffers may delay the availability of data in the buffers to the output for a period corresponding to the delay between the fastest and slowest transmission path. In this manner, data only becomes available to the output, when corresponding user content has been receiver on all the paths. At this point, the data in the buffers (comprising the content) may be made available to the output 111 for rendering.

Delaying the respective data streams may comprise storing received data in a respective data buffer. In the example of FIG. 1, the first path 122, 132 has the shortest processing delay and is the first to start receiving data. The received data stream on the first path is written to the first delay buffer 141. A write pointer 141 a of the first delay buffer 141 indicates an amount of data that has been written to the first buffer. The delay between the first and second paths is (B-A) and so the first path 132 receives data for a period of (B-A) before the second path starts receiving data comprising corresponding user content. When data is received on the second path 133, it is written into the second delay buffer 142. A write pointer 142 a indicates the amount of data that has been written to the second buffer.

The delay between the first and third paths is (C-A) and so the first path 132 receives data for a period of (C-A) before the third path starts receiving data comprising corresponding user content. The delay between the second and third paths is (C-B) and so the second path 133 receives data for a period of (C-B) before the third path 134 starts receiving data comprising corresponding user content. A write pointer 143 a indicates the amount of data written to the third buffer.

FIG. 1 depicts the state of the delay buffers 141, 142 and 143 when a first unit of a data stream comprising the content is received and stored in the third buffer 143. At this point, the first receive path 132 has been receiving the content for a time period of (C-A) and the second receive path 133 has been receiving the content for a time period of (C-B) and the third receive path 134 has just received its first unit of the content. At this point at least a portion of the content is available in all three of the delay buffers 141, 142 and 143 and so the data in the delay buffers 141, 142 and 143 becomes available for selection to be provided to the output 111. In this example, the buffers are arranged as first-in first-out (FIFO) buffers, however, it will be appreciated that the buffers may take any suitable form.

The read pointers of each buffer 141, 142 and 143 may indicate the next portion of data to be read from the respective buffers. The read pointers of the three buffers 141, 142 and 143 may be synchronised so that they simultaneously point to respective portions of data in the respective buffers that comprise corresponding content. The read pointers may be updated simultaneously as data is processed from at least one of the data streams. This may allow them to remain synchronised. In this manner, if the receive paths are switched between (the switching mechanism 112 couples a different buffer to the output 111) the read pointers of all the buffers point to the same or corresponding position with respect to the content.

The implementation of the buffer size will be dependent on the amount data that needs to be stored for a data stream. This, in turn, is dependent on the size of the data itself as well as the maximum delay between streams. This may result in a system requirement of a large amount of memory. Some systems are limited in the amount of memory that can be provided. For example, an embedded system may have restricted memory space and thus may not be able to provide the requisite amount of memory.

Embodiments of the present application are related to a receiver device that outsources the receive buffers to a further device. In one example, the receive buffers may be outsourced to a host device. The receiver device may store incoming data streams at the host device and request the retrieval of portions of the received data streams for further processing and output.

FIG. 2 shows an example of a multi-source receiver 210 that may receive data streams from multiple sources and delay the data streams by providing them to be stored at a host device.

FIG. 2 shows a receiving device 210 having a first receiver 211, a second receiver 212 and a third receiver 213. It will be appreciated that the first, second and third receivers may be similar to those of FIG. 1 and may be configured to receive data streams from respective transmit paths such as those transmitted by a transmitter, for example transmitter 120.

The first receiver 211 is coupled to a first portion buffer 214, the second receiver 212 is coupled to a second portion buffer 215 and the third receiver 213 is coupled to a third portion buffer 216. The receiving device 210 may further comprise a memory 217. It will be appreciated that the receiving device 210 may further comprise a processor or controller for controlling the receiver. It will be appreciated that the controller may be configured to cause the reception device to carry out any method steps discussed herein.

The receiving device 210 may receive a plurality of data streams from a plurality of sources, where each of the data streams comprise corresponding content. Each of the data streams may be received on a respective one of the receive paths, each comprising a receiver 211, 212, 213 and portion buffer 214, 215 and 216. Like in the example of FIG. 1, the data streams may be buffered and delayed in order to align the corresponding content within the data streams. However, unlike the example of FIG. 1, the delay buffers may be implemented at a host device.

A host device 220 is shown in FIG. 2 comprises a first delay buffer 221, a second delay buffer 222 and a third delay buffer 223. In functionality, the delay buffers 221, 222 and 223 may correspond to the delay buffers 141, 142 and 143 of FIG. 1. In particular, each of the first, second and third delay buffers 221, 222 and 223 may be configured to store one of the data streams received by the receiving device. Each of the delay buffers 221, 222 and 223 may comprise a respective write pointer 221 a, 222 a and 223 a pointing to the next position in the buffer to be written to. Each of the delay buffers 221, 222 and 223 may further comprise a respective read pointer 221 b, 222 b and 223 b. Each of the read pointers may point to a position of corresponding content within the respective buffers.

The receiving device 210 may periodically transmit 230 received data to the host device 220 to be stored in the respective buffers. The host device 220 may receive the transmitted data and store it in the relevant buffers. The receiving device may further transmit 230 a request for stored data from the delay buffers to the host device 220. The host device 220 may read stored data from the delay buffers and provide 240 this to the receiving device. The receiving device may then further processes the data to be output. It will be appreciated that the data read from each of the delay buffers may contain corresponding content as pointed to by the synchronised read pointers 221 b, 222 b and 223 b.

The receiving device 210 may control the storage and retrieval of data from the host device. The receiving device 210 may do this by storing information relating to the delay buffers at the receiving device 210 at memory 217. For example the receiving device 210 may store information relating to the read pointers 221 b, 222 b, 223 b and the write pointers 221 a, 222 a, 223 a and provide this information with the request for data.

In operation, the receiving device 210 may receive three data streams on the three data paths. The received data for each stream may be stored in a respective portion buffer 214, 215, 216. In some examples, the receiving device may carry out some processing on one or more of the received data streams before storing them in the portion buffers. The receiving device 210 may then send a request 230 to the host device to store the data received at the receiving device 210 for each stream.

In one example, a request 230 to the host device 220 may be made once a prerequisite amount of data has been received and stored in a portion buffer for at least one of the data streams. For example, the reception device 210 may receive a portion of data for each receiver path every n milliseconds. The amount of data received before the receiving device 210 forwards the data portions to the host device 220 may be balanced in order to minimize both the size of the portion buffers and the number of messages sent to the host device 220 forwarding the data portions. In one example, where one or more of the receive paths are digital audio broadcast (DAB) paths, the prerequisite portion of data may correspond to a DAB frame and for example, be available every 24 milliseconds. Once a portion of data is received for each data stream, the portions of data stored in each of the portion buffers 214, 215, 216 may be forwarded to the host device 220 for external storage. In this example the data portion for each data stream is sent simultaneously or synchronously in order to reduce the number of messages sent between the receiving device 210 and the host device 220.

The message 230 comprising the data portions to be stored, may further comprise a request for stored or delayed data to be returned to the receiver. This delayed data may correspond to data requested by the receiving device 210 for further processing and output to a user, for example via a loudspeaker.

The receiving device 210 may control the storage and retrieval of the data portions or blocks to the host device 220. For example, the receiving device may store indexing data relating to the position of the data in the delay buffers 221, 222 and 223. In one example, a memory 217 may store read and write pointer information and the request 230 may comprise this address information indicating where in the delay buffers to write the forwarded data and where to read requested data. The pointer information in the memory 217 may be updated with each request to write data to the delay buffers and read data from the delay buffers.

In response to the request 230, the host device may send a message 240 comprising the requested delayed data portions for each of the data streams. In this example a communication exchange comprising a combined forwarding of received data portions and requests for delayed data portions 230 as well as a response comprising the requested data portions will take place every time a portion of data is received for each data stream at the receiving device 210. In the example of DAB, this communication exchange may take place every 24 ms.

FIG. 3 is a flow diagram depicting the method steps according to one example. At step 301, a receiving device receives a portion of data for each data stream. The data streams carry corresponding content which may be offset to each other with respect to time. When at least a portion of the data is received on each stream, the method may progress to step 302.

At step 302, the receiving device may send a first message to the host device. The first message may comprise a forwarding message which forwards the received data for the data streams to a host device for storage. The message may contain the received portions of data on the data streams as well as indexing information which indicates where the host device is to store the forwarded portions. The host device may store the forwarded data portions in respective delay buffers corresponding to each of the data streams. The indexing information may include write pointer information indicating to the host device where the data portions are to be written in the delay buffers.

In some examples the receiving device may additionally include a request message in the first message. The request message may comprise a request for delayed data stored in the delay buffers at the host device. The request message may include indexing information. In this case, the indexing information may include read pointer information indicating to the host device where the requested data is to be read from the delay buffers.

At step 303, the receiving device may update the indexing information. The indexing information may be stored at the receiving device and maintained by the receiving device. The write pointers may be updated to point to the next available space in the delay buffers to be written to. The read pointers may be updated to point to the next point in the delay buffers to be read from. It will be appreciated that each of the read pointers will point to corresponding user content in the delay buffers. In order to do so, the receiving device may calculate a delay between user content of the data streams and adjust the respective read pointers with respect to this delay.

At step 304, the receiving device may receive a second message from the host device comprising the requested data portions. The receiving device may then provide the data portions for further processing and/or rendering one or more of the data portions to the output.

FIG. 4 shows a further example of an embodiment. In the example of FIGS. 2 and 3, an example three data streams are depicted as being received by the reception device 210. Portions of data from each stream are stored in a delay buffer at a host device 220. The reception device 210 may request portions of data from the delay buffers in the host device 220 by providing the host device 220 with indexing data for the requested data portions.

In the example of FIG. 4, a host device may be further configured to receive an auxiliary data stream and provide data portions of the auxiliary data stream to the reception device 210. This may be useful in the case where, for example, the auxiliary data stream is an Internet protocol (IP). In this example, the auxiliary data is delayed with respect to the data streams received by the reception device. In other words, the auxiliary data stream may experience a transmit and processing delay that is greater than the delay experienced by the other data streams. For example an IP data stream may experience delays that are greater than an FM or DAB data stream. Data content carried by the auxiliary stream may be received at after corresponding data content is received on the other data streams received by the reception device 210.

FIG. 4 shows a reception device 210 and a host device 420. It will be appreciated that parts of the reception device 210 and host device 420 may be similar to the reception device 210 and host device 220 depicted in FIG. 2 and that, in this case, like reference numerals may refer to like features.

The host device 420 has a first, second and third delay buffer 221, 222 and 223 for storing data portions received on a respective first, second and third data stream 211, 212 and 213 and received in a message 230 from the reception device 210. The host device 420 may further comprise an auxiliary input 401 for receiving an auxiliary or additional data stream. In one example, the auxiliary data stream may be an IP stream received via a network to which the host device 420 is coupled.

The data stream received on the auxiliary input 401 may be stored in an auxiliary buffer 403. The host device 420 may also comprise an optional sample rate converter 402. In some examples, the data streams 211, 212 and 213 may be considered to have the same sample rate. The auxiliary data stream may have another sample rate. In examples, the sample rate of the auxiliary data stream 401 may be converted to be the same as the sample rate of data stream 211, 212 and 213. This may ease a processing burden when processing the respective streams. It will however be appreciated that the sample rate converter 402 may be optional. In some cases differences in sample rates may be dealt with in the processing of the data streams. It will also be appreciated that the data streams 211, 212 and 213 need not necessarily have the same sample rates and similar measures, for example sample rate conversion or data stream processing, may be applied to them.

The example of FIG. 4 may operate similarly to that of FIG. 2. For example, after a portion of the data streams 211, 212 and 213 have been received, the reception device 210 may send a first message 230 to the host device. The first message may comprise a request to store the data portions and may include indexing data associated with the data buffers 221, 222 and 223. The first message 230 may further constitute a request for delayed data from the data streams 211, 212 and 213.

In response to the first message 230 or request, the host device may respond with a second message 440 comprising the requested delayed data from the buffers 221, 222 and 223. If a data portion is available in the auxiliary buffer 403, then that data portion received on the auxiliary data stream may be provided to the reception device 210 in the second message 440.

It will be appreciated that while the requested data portions for the data streams 211, 212 and 213 comprise data portions that have been delayed by the buffer, the data portion from the auxiliary data stream may not be delayed. This may be because the auxiliary data stream 401 may have the longest delay with regards to the corresponding content carried on the data streams 211, 212, 213 and 401. In other words, the content received by the auxiliary data stream 401 may already have been received on the data streams 211, 212 and 213 and thus need not be further delayed.

It will be appreciated that the required size of the buffers 221, 222 and 223 may depend on the amount of delay to the data stream that a buffer is to introduce. The auxiliary buffer may be smaller than the buffers 221, 222 and 223 as the auxiliary buffer need only buffer a portion of the data stream 401 for the time taken in one communication round. In this case a communication round comprises the time for the message 230 to be sent and replied to with message 440. A data portion may be read from the auxiliary buffer 403 in each communication round.

With reference to FIG. 3, in the example in accordance with FIG. 4, the reception device 210 will additionally receive a data portion from the auxiliary data stream at step 304. At step 305, the reception device may further select from the received data portions, including the data portion on the auxiliary data stream, for rendering. The example of FIG. 4 has been described with the reception device 210 providing no indexing information for the auxiliary data buffer or data stream. This is appropriate in embodiments where the corresponding content is received on the data streams 211, 212 and 213 before being received on the auxiliary data stream 401 and the data buffers 221, 222 and 223 delay the data streams accordingly. In other examples, the reception device may also provide explicit indexing information for the auxiliary data stream and/or buffer. This indexing information may for example related to dynamic buffer sizing and/or may control the fill level of the auxiliary buffer. In some further embodiments, the indexing information may control a delay to the auxiliary data stream in the auxiliary buffer and/or may indicate or set a size of the data portion to be provided in the message 440.

In an example, the auxiliary buffer 403 may be used for processing such as equalling out side effects from reception jitter or sample rate conversion. It may allow consideration for advanced decision logic, like error handling, when its fill level is being constantly monitored by the reception device.

In the foregoing, the reception device 210 has been described as storing and maintaining indexing information for the buffers 221, 222 and 223. As described, this indexing information may comprise read and write pointers or information as to where to next write in the buffer and where to next read from in the buffer. In a further example, the reception device 210 may further store and maintain meta information associated with the data streams. This meta information may for example comprise quality information relating to the quality of the data portions being received on each data stream and being stored at the host device 220.

For block-based audio streams, data portions carried by each of the data streams 211, 212 and 213 may arrive periodically at the reception device 210. In the case of a reception issue, a gap in the reception of data portions for one or more of the data streams may occur. In an extreme example, no data at all may arrive in a periodic reception window for a data stream. In other examples, data received for a data portion may be (partially) defective or fully received. The reception device 210 may be aware of properties such as these for a data portion on reception of the data portion—for example before the data portion is sent for storage and/or received to be rendered.

Information regarding the quality of a data portion can be considered to be meta-information. This meta information may for example be stored along with the actual data portion. Once the data portion is to be used, the associated meta-information stored alongside the data portion may be assessed for use in the selection and rendering of a data portion. For example the meta information may be used to decide whether the associated data portion may be decoded or should rather shall be omitted because it is faulty or missing data. Advanced error concealment processing may also be carried out on the basis of this meta-information, for example gradually fading out still good audio and/or switching data streams to be rendered based on upcoming reception gaps.

In the present application, the delay buffers may be outsourced to a host device 220, 420. In the case where meta information is stored alongside the data portions, this meta information is not immediately accessible to a reception device 210 due to the communication delay between the reception device 210 and host device 220, 420. Furthermore, requesting a delayed data portion from a host and receiving said data portion and associated meta information before being able determine that the data portion should be discarded increases the communication overhead.

A further example of a reception and host device is provided according to FIG. 5 in which meta information corresponding to received data portions is stored in the reception device 210. This may allow the reception device 210 to make decisions regarding which of the data portions carrying corresponding content to render or process further and which to discard. In some examples, the reception device 210 may further selectively request which buffers 221, 222, 223 to be read from.

FIG. 5 shows a portion of the reception device 210 and host device 220 where meta information is stored at the reception device 210 for data portions stored at the host device 220.

FIG. 5 shows the portion of the reception device 210 comprising a memory 217. The memory 217 comprises indexing information 520 and meta information 510 associated with data portions stored in the host device 220. The portion of the host device 220 comprising a data buffer 221 is shown. It will be appreciated that while indexing and meta information and a data buffer is shown only for the first data stream 221, similar provisions are made for the other data streams.

Each stored data portion in the data buffer 221 may be associated with indexing information 520 and meta information 510. This is shown by the associated 530. It will be appreciated that in some examples indexing and/or meta information may be the same for more than one consecutive data portion.

FIG. 5 further shows an example of meta information 510. In this example, the meta information may comprise a plurality of fields, for example an indication whether the data portion comprises audio or is empty (Audio/Empty 502), error information associated with the data portion (Error Information 503), the audio standard to which the portion relates (Audio Standard 504), one or more properties of the data portion (Audio Properties 505) and further optional additional fields 506. The additional fields 506 may include an indication of the size of each delayed data portion stored at the host device. The size may indicate the duration of the audio contained within the delayed data portion. The size may indicate the size of the delayed data portion in terms of the quantity of data thereof. For example, for variable bit rate encoded audio, the duration of the audio for an amount of data for the delayed data portion may be dependent on the bit rate used to encode that audio.

Referring to FIG. 3, in operation the reception device 210 may determine meta information from the received data portions before forwarding them to the host device for storage at step 302. The reception device 210 may further determine from the meta information 510 which data portions to request at step 302 and send indexing information accordingly. The reception device 210 may be able to look-ahead with respect to the available quality of the delayed data stream based on the meta-information for externally stored data portions. The reception device 210 may pre-decide whether a data portion would be suitable for rendering and/or is needed.

In the example of FIG. 5, the reception device 210 may request delayed data portions from selected data streams or buffers. It will be appreciated that in other example this is also possible and the reception device need not request data portions from all the data buffers.

The foregoing describes a portion of data being received for each of the data streams at the reception device before those portions are sent to the host device for storage. It will be appreciated that the amount of data making up a portion of data may be determined in dependence on the nature of the data streams received by the reception device. For example, if one of the data streams transmits data according to a DAB standard, the data portion may correspond to a maximum size for a DAB frame.

In another example, and as illustrated in Figured 6, one or more data streams may be transmitted in accordance with DAB+ which comprises DAB super frames, shown as stream 602 in comparison to DAB frames as stream 601. In one example these super frames may be received in 120 ms corresponding to five consecutive DAB frames of 24 ms each. For a DAB+ stream, a data portion may be selected to correspond to the super frame size or corresponding to a subset of the super frame for example. In another example, one of the data streams may be transmitted in accordance with T-DMB in which case the transmitted frames may vary in size, T-DMB frames are illustrated as stream 603. In this case a data portion size may be selected on a for example maximum frame size or using other criteria. FIG. 6 illustrates addressable locations of the delay buffers. Stream 601, illustrating DAB shows receipt of frames each containing 24 ms of audio at regular intervals. Stream 602, illustrating DAB+, shows receipt of frames containing 120 ms of audio and empty slots or addressable locations therebetween compared to the DAB stream 601. Stream 603, illustrating T-DMB shows variable audio length frames (also termed “containers”) that may be received at different time points.

It will be appreciated that the requesting of delayed data portions from the host device may be challenging, particularly when the size of the delayed data portions may be variable. Also, the content of the delayed data portions may be subject to block based encoding and therefore, a whole block, which may correspond to a delayed data portion, may be required for the content encoded therein to be decoded. In addition, the communication between the host device 220 and the reception device 210 may be subject to technical limitations in terms of the bandwidth available, the maximum size of the data that may be transferred at one time as well as communication delays.

It will be appreciated that the choice of the size of the data portion which is to be received by the reception device and then forwarded to the host for storage may be dependent on the transmission standard(s) being received at the reception device. In some examples, the data portion size may correspond to a maximum frame size of at least one of the standards or may be another predetermined size. The data portion size may be fixed for all of the received data streams in some examples. This may simplify the storage and retrieval of data portions from the data buffers. For example, a data portion is available at the reception device on all the data streams at the same time. In other examples, a data portion size may be selected for individual data streams and may be tailored to the transmission standard of each stream.

In the foregoing a communication round has been depicted as a first message forwarding a plurality of data portions to a host device for storage and a request for stored data portion(s) to be retrieved from the host device. The forwarding of the plurality of data portions to the host device for storage may not form part of a communication round in one or more examples. The forwarding of the data portions to the host device may be performed by a different process or apparatus. The request may form part of the first message or may be sent separately. A second message is returned from the host comprising the requested data. It will however be appreciated that in some cases, the communication round may omit the request for data from the host device. For example, in some communication rounds, the reception device may not require more data, for example independence on a buffer fill status at the reception device for data to be rendered.

In the foregoing it has been described that the reception device may identify data portions to be retrieved from the host device in dependence on meta information stored at the reception device and associated with the data portion. It will be appreciated that such identification may be made in dependence on additional or alternative factors. For example, the identification may also be based on a buffer fill level at the reception device or a preferred data stream in the case that data portions are of similar quality. For example, the reception device may prioritise data portions from the currently rendered data stream rather than having to swap back and forth between the streams excessively.

It will be appreciated that the reception device and the host device will comprise an interface for communicating between them. For example, each of the reception device and host device may comprise and input and output port for sending and receiving messages, for example during a communication round.

In one or more examples, it may be necessary to move to a different temporal position in the content. For example, when switching between streams, it may be desirable to switch at a time-matched time point when corresponding content at a corresponding time is available. In other examples, it may be desirable to change time point within the content of a stream that is currently being presented to a user, such that it is time aligned with the content of one or more other streams.

Moving to a different temporal position may be considered more generally as adding an arbitrary delay to the data stream. As discussed above, this may be achieved by moving the read pointer in time. In examples where the stream is block-based and the blocks correspond to a data portion, the moved read pointer might point into the middle of a data portion. Hence, the whole data portion may have to be decoded first (because that is the nature of block-based encoded data portions) and then the offset within the data portion may be translated into an offset with respect to the content, i.e. in the decoded domain. Usually, decoded data that belongs time-wise before the moved read pointer will be dropped. The remainder, when rendered, eventually reflects the correctly adjusted arbitrary delay.

When the data of the data streams is stored at a host device 220 and may need to be sequentially requested, the adding of arbitrary delays may be more challenging. Further, variable blocks sizes and limitations on the amount of data that may be transferred from the host device 220 to the reception device 210 in each communication round may add to the challenge. It may also be appreciated that if the addition of an arbitrary delay is attempted during the playback or decoding of the delayed data portions, there may also be a time pressure to the retrieval of arbitrarily delayed data portions. In particular, the amount of data to be transferred for the delayed data portions that include the time point based on the arbitrary delay may take a certain transfer time but only a limited time may be available until playback of the arbitrarily delayed content is required.

Further, when the content of the delayed data portions is being presented to a user it may be desirable to avoid gaps in playback when adding the arbitrary delay. Accordingly, we describe an example controller that operates to reduce or avoid playback gaps in view of one or more of the technical limitations mentioned above.

FIG. 7 shows an example reception device 701 and host device 702. As in the previous examples, the host device 702 include a plurality of delay buffers 703, 704, 705 configured to receive portions of data from a plurality of data streams carrying respective content forwarded thereto from the reception device 701. The reception device 701, in this example, includes the controller 706 configured to request delayed data portions from the delay buffers 703-705 of the host device 702 for decoding of the delayed data portions. The controller 706 is shown configured to receive indexing information from a memory 707, the indexing information providing at least an indication of time points in the content of each of the data portions in the delay buffers 703, 704, 705.

The controller 706 may request the delayed data portions, stored in addressable locations 708 of the delay buffers of the host device 702. The reception device 702 or, for example, the communication 710 between the host device 702 and the reception device 701 may be configured such that each delayed data portion received by the reception device 701 from the host device 702 in response to each request of the controller 706 is received as a plurality of consecutively received sub-portions. For example, the communication 710 between the host device 702 and the reception device 701 may have a limited bandwidth. As discussed above, the size of DAB frames, DAB+ frames and T-DMB may all differ and also T-DMB containers may each vary in size. A delayed data portion may comprise one DAB frames, one DAB+ frames or one T-DMB container. Accordingly, each sub-portion may comprise a subset of the content of the delayed data portion. The receipt of each sub-portion from the host device 702 may take at least a predetermined transfer time over the communication channel 710. The delayed data portions may be block based encoded meaning that individual sub portions may not be decodable individually. Accordingly, the sub-portions of a whole delayed data portion may be required before decoding of the delayed data portion can be performed.

Thus, the controller 706 may make requests to address the addressable locations 708 of the delay buffers. The addressable locations may include data portions of varying size or the same size that may need to be transferred to the reception device as a plurality of sub-portions over a corresponding plurality of communication rounds. The controller 706 may provide for forwarding of delayed data portions or sub-portions thereof received from the host device 702 to a decoder 711. The decoder 711 may provide for decoding of the delayed data portions. The decoder 711 may include buffers (not shown in FIG. 7 but described later) in which to accumulate sub-portions of one or more of the delayed data portions until a whole delayed data portion has been received and is therefore decodable. Once all the constituent sub-portions are received, the decoder 711 may be configured to decode the delayed data portion. The decoder 711 may provide the decoded delayed data portions to a content renderer 712 for presentation of the content of the decoded delayed data portions to a user. In one or more examples, the content renderer 712 may comprise an audio renderer for a radio.

FIG. 8 shows an example operation of the reception device 701 and is broadly similar to FIG. 7. The same reference numerals have been used for like parts. The controller 706 has been omitted for clarity. The host device 702 is shown with only one delay buffer 703 for clarity.

The decoder 711 is shown having a decoder-in buffer 801 for receiving sub-portions from the host device 702. When the decoder-in buffer 801 has received all of the sub-portions of a delayed data portion, it provides the whole delayed data portion to a decoder processor 802 for decoding. The decoded content of the delayed data portion is then provided to a decoder-out buffer 803. The decoder-out buffer 803 provides the decoded content to the content renderer 712.

The content renderer 712 is configured to provide for presenting of the decoded content. For understanding only, the content renderer 712 is depicted with a rendered content indicator 804 to illustrate parts of the content that have been rendered. In other examples, the function of the decoder-out buffer 803, to hold decoded content for forwarding for rendering, may be performed by a buffer external to the decoder 711. It will be appreciated that different hardware configurations may be possible and the operation of the controller 706 described hereinafter may be applied to the present and different hardware configurations.

Looking at the host device 702, each addressable location is shown with a number therein. The number represents the size of the delayed data portion stored at that location in terms of the number of communication rounds it will take to transfer it to the reception device. Accordingly, all except one location is shown with a number 5 illustrating that five communication rounds will be required to transfer the content therein to the reception device 711. The host device 702 is also shown with read pointers 805 and 806 illustrating which delayed data portions are requested by the controller 706. The read pointer 805 comprises a current read pointer, R, illustrating the delayed data portion currently being retrieved and decoded and presented to a user. The time represented by the current read pointer 805 may be an example of a first time point. The read pointer 806 comprises a new-position read pointer, R′, illustrating the location of the time point the controller 706 is attempting to move to by way of adding an arbitrary delay. This time point may be provided to the controller 706 as a request. The controller 706 may thus be configured to action the request or “instruction to change time points” by providing delayed data portions that contain the instructed time point to the decoder 711. The time represented by the new-position read pointer 806 may be an example of a second time point. The new-position read pointer 806 thus shows which delayed data portion contains the second time point and, by virtue of its left-right position within one of the addressable locations 708, the approximate position within the content encoded in said delayed data portion.

FIG. 8 illustrates an example situation in which delayed data portions are being retrieved from the host device 702 for decoding. Accordingly, the current read point 805 and the number “2” in the addressable location 807, as well as the number “3” in the decoder-in buffer 801, shows that the reception device 701 has received three of five sub-portions for the delayed data portion of location 807. Accordingly, two sub-potions are still to be retrieved from the location 807 before the decoder-in buffer has a whole delayed data portion. Further, the audio decoder processor 802 has decoded the previously received delayed data portion and it is partially present in the decoder-out buffer 803. In fact, in this example, there are two communications rounds worth of content available in the decoder-out buffer 803 (shown by the number “2” in the decoder-out buffer 803) and the content renderer 712 has rendered three communications rounds worth of content (shown by the number “3” in the rendered content indicator 804). It will be appreciated that the duration of the content available is presented in terms of the number of communication rounds wherein the communication rounds each take a predetermined transfer time.

In general, the controller 706 may provide for rendering content from decoder-out buffer 803 by the content renderer. If the decoder-out buffer 803 is empty, the decoder processor 802 is configured to decode another block from decoder-in buffer 801. If the decoder-in buffer 801 is empty, the controller 706 may provide for requesting of the next delayed data portion from host device 702 (in multiple communication rounds if required) at the position of the current read pointer, R 805.

FIG. 9 illustrates the operation of such an arrangement without the use of an embodiment of the controller 706 of the disclosure. In FIG. 9, the current read pointer R is moved to the start of the addressable location of the delayed data portion that contains the second time point, marked by the new-position read pointer R′ 806. It will be appreciated that even though the second time point may reference a time some point through the content of the delayed data portion, the whole delayed data portion may be required to be retrieved for it to be decodable.

The decoder-out buffer 803 still has two communication rounds of decoded content therein for providing to the content renderer 804. The decoder-in buffer 801 had only three sub-portions of a total of five sub-portions therein and therefore does not have enough sub-portions to provide for decoding. Accordingly, the decoder-in buffer may be emptied given it is not holding decodable content and may await receipt of sub-portions from the host device 702 in accordance with the position of the moved current read pointer R 805.

It will take five communication rounds to fill the decoder-in buffer 801 with the sub-portions to provide a decodable delayed data portion, as illustrated by the number “5” in the location 900. However, after two communication rounds the decoder-out buffer 803 will be empty and therefore the user may be presented with silence i.e. no content is available for a further three communication rounds until the delayed data portion at location 900 is provided to the decoder-in buffer 801.

It will also be noticed that the delayed data portion at location 900 takes five communication rounds to transfer but once transferred, the second read pointer R′ will have moved to the next delayed data portion 901. It will be appreciated that the read pointers 805, 806 move through the delayed data portions as time passes as the retrieval of data portion is a live process. Thus, the content available for playback will not have the required arbitrary delay indicated by the second read pointer R′ 806. Thus, once retrieved, the delayed data portion at location 900 will be already out of date.

FIG. 10 illustrates the operation of such an arrangement with the use of the controller 706 of an embodiment of the disclosure. FIG. 10 continues from the situation shown in FIG. 8. FIGS. 10 to 21 illustrate the actions of the controller 706 that may reduce any interruptions or gaps in the presentation of content to a user. In particular, the figures illustrate that while requesting and/or receiving the delayed data portions from the second time, the controller provides for requesting of one or more delayed data portions corresponding to the first time, which may provide content for presentation to a user while the delayed data portions from the second time are transferred from the host device.

Looking now at FIG. 10, the controller 706 (shown in FIG. 7) uses a further read pointer R″ 1001. The further read pointer 1001 is used to continue the retrieval of sub-portions from the delayed data portion relating to the first time i.e. at location 1002. As mentioned above, the decoder-in buffer 801 includes three sub-portions at the time a request to switch to a different time point is received by the controller 706. The remaining sub-portions of the delayed data portion at location 1002 may continue to be received by addressing the location pointed to by the further read pointer 1001, as will be described in more detail below.

The controller 706 is configured to identify one or more second-time-point delayed data portions to request from the host device 702. The identification of which delayed data portions to request from the host device 702 is based on the second time point referenced in the request to switch instruction received by the controller 706 and indexing information stored in memory 707. Thus, the indexing information may be used to identify a delayed data portion or addressable location thereof 900 that contains the content in which the second time point is located. Similar to as shown in FIG. 9, the controller then selects the delayed data portion at the location 901 directly subsequent thereto.

In FIG. 10, the new-position read pointer R′ 806 marks the delayed data portion identified based on the second time point referenced in the request to switch and the indexing information.

The read pointer R 805 may be moved to the start of the delayed data portion subsequent to that referenced by the new-position read pointer R′ 806. In this example, there are two communications rounds worth of content available in the decoder-out buffer 803 (shown by the number “2” in the decoder-out buffer 803) and the content renderer 712 has rendered three communications rounds worth of content (shown by the number “3” in the indicator 804). As the controller 706 provides the further read pointer 1001 to continue the transfer of the sub-portions at location 1002, the decoder-in buffer 801 is maintained with the three sub-portions already received at the time of the request to switch, unlike the example shown in FIG. 9.

In this example, the step of identifying the one or more second-time-point delayed data portions to request from the host device 702 is further based on the total transfer time of a delayed data portion at location 901 subsequent to the delayed data portion at location 900, which contains the second time point, marked by pointer 806.

FIG. 10 illustrates the identification of a first candidate delayed data portion 901 comprising the delayed data portion directly subsequent to the delayed data portion containing the second time point marked by pointer 806. The controller 706, based on metadata 709 in memory 706 (shown in FIG. 7) indicative of the size of the delayed data portions in the delay buffers 703-705, may determine the total transfer time of the first candidate delayed data portion 901. In this example, the total transfer time is five communication rounds.

If the total transfer time of the first candidate delayed data portion at 901 is less than the time between the second time point marked by pointer 806 and a time point 1003 defined by the start of the content of the first candidate delayed data portion at 901, the controller is caused to identify said first candidate delayed data portion 901 as the second-time-point delayed data portion. In this example this is not the case, because the total transfer time of the first candidate delayed data portion at 901 is five communication rounds and new-position read pointer, R′ 806 points to a position two communication round prior to time point 1003.

Accordingly, the total transfer time of the first candidate delayed data portion 901 is greater than the time between the second time point marked by 806 and the time point defined by the start of the content of the first candidate delayed data portion, marked at 1003. The practical effect of such a situation is that by the time the first candidate delayed data portion 901 is retrieved (5 communication rounds) the second read pointer will have progressed to a time point within the first candidate delayed data portion 901. Accordingly, much of the content of the first candidate delayed data portion 901 will be out of date and continued retrieval may result in playback gaps. Thus, in this example, the controller 706 is caused to identify a delayed data portion at 1004 received subsequent to the first candidate delayed data portion at 901 as the second-time-point delayed data portion.

In one or more examples, the delayed data portion at 1004 may be considered a second candidate delayed data portion and the above-mentioned test may be repeated. If the test were repeated, the total transfer time for the second candidate delayed data portion at 1004 is five communication rounds. The time between the second time point marked by 806 and the time point defined by the start of the content of the second candidate delayed data portion at 1004, is seven communication rounds. Accordingly, the second candidate delayed data portion at 1004 is identified as the second-time-point delayed data portion, which is to be retrieved from the host device by the controller 706.

FIG. 11 shows the situation one communication round later than the situation shown in FIG. 10. Accordingly, the content renderer 712 has rendered a further communication rounds worth of content from the decoder-out buffer 803. There remains one communication round worth of content in the decoder-out buffer 803.

FIG. 11 shows the current read pointer, R, 805 placed at the start of the identified second-time-point delayed data portion at 1004 ready for the controller to begin retrieving the sub-portions thereof. In addition, the further read pointer 1001 is positioned at the location of current read pointer 805 when the request to change time point arrived.

FIG. 11 also illustrates the provision of a second decoder-in buffer 1100 to receive the sub-portions of the second-time-point delayed data portion at 1004.

The controller 706 may be configured to determine for how long or the number of requests required to retrieve the delayed data portions from both the first time and the second time. The controller 706 may be configured to determine the total transfer time for receiving the one or more identified second-time-point delayed data portions at 1004 using meta information from memory 709 indicative of the number of sub-portions required to receive the one or more identified second-time-point delayed data portions at 1004. In this example, the total transfer time is five communication rounds for the identified second-time-point delayed data portion at 1004. The controller 706, based on the determined total transfer time of five communication rounds may determine the one or more requests required of the one or more delayed data portions at 1005 corresponding to the first time or times consecutively subsequent thereto in order to continue decoding said delayed data portions at the first time while the one or more identified second-time-point delayed data portions are received from the host device. In this example, as shown in FIG. 11, retrieval of two sub-portions of the delayed data portion of the first time point at 1005 provides five communication rounds worth of content because the decoder-in buffer 801 already contains three sub-portions. In addition, the decoder-out buffer 803 already contained two communication rounds worth of content (as shown in FIG. 10). Accordingly, the controller 706 may be configured to determine that continued retrieval of the delayed data portion at 1005 provides sufficient playback time (seven communication rounds worth) to retrieve the delayed data portion at the second time at 1004 and the retrieval of a data portion subsequent to the first data portion, such as at 1106, is not required in this instance. Thus, the controller may sum the duration of decoded content available in the decoder-out buffer 803, the duration of content available in the decoder-in buffer 801 and the duration of content still to be retrieved from the delayed data portion at the first time point. If the sum of the duration of the content is greater than the time required to retrieve the second-time-point delayed data portion then the controller 706 knows to only retrieve the remaining sub-portions from the delayed data portion at the first time point at 1005. If said sum was less than the time required to retrieve the second-time-point delayed data portion at 1004 then the controller 706 knows it is required to retrieve the remaining sub-portions from the delayed data portion at the first time point at 1005 and at least one delayed data portion directly subsequent thereto such as the delayed data portion at 1106.

The controller 706 therefore requests the identified second-time-point delayed data portion at 1004 from the host device and, in this example, also continues to request the delayed data portions at 1005 corresponding to the first time. FIG. 11 shows the decoder-out buffer 803 with only one communication round of content remaining therein.

FIG. 12 shows the situation after one further communication round following the situation shown in FIG. 11. Accordingly, the content renderer 804 has rendered a further communication rounds worth of content from the decoder-out buffer 803. The decoder-out buffer 803 is now empty and the content renderer 804 has one communication rounds worth of content to present.

The next sub-portion from the delayed data portion at 1005 has been provided to decoder-in buffer 801. Accordingly, decoder-in buffer 801 now has four sub-portions therein and the location 1005 has one sub-portion left to transfer thereto. Accordingly, the delayed data portion at 1005 is shown with a number “1” to illustrate that there is one sub-portion left to transfer. The second decoder-in buffer 1100 has received a first of five sub-portions from the delayed data portion at 1004. Accordingly, the second decoder-in buffer 1100 is shown with a number “1” indicating it has received one sub-portion and the delayed data portion at 1004 is shown with a number “4” to illustrate that there are four sub-portions left to transfer.

FIG. 13 shows the situation one communication round later than the situation shown in FIG. 12. Accordingly, the content renderer 804 has finished rendering the last portion of content from the decoder-out buffer 803 received in FIG. 12. The decoder-out buffer 803 is now empty but the decoder-in buffer 801 now holds a whole delayed data portion and is therefore decodable.

Thus, the final sub-portion from the delayed data portion at 1005 has been provided to decoder-in buffer 801. Accordingly, decoder-in buffer 801 is shown with five sub-portions therein and the delayed data portion at location 1005 has transferred completely. Accordingly, the delayed data portion at 1005 is shown without a number to illustrate that it is wholly transferred to the reception device. The second decoder-in buffer 1100 has now received two of five sub-portions from the delayed data portion at 1004. Accordingly, the second decoder-in buffer 1100 is shown with a number “2” indicating it has received two sub-portions and the delayed data portion at 1004 is shown with a number “3” to illustrate that there are three sub-portions left to transfer.

FIG. 14 shows the situation during the same communication round as FIG. 13. In FIG. 14, the audio decoder processor 802 is shown having received the whole block from decoder-in buffer 801, decoded it and provided it to the decoder-out buffer 803. The decoded delayed data portion in the decoder-out buffer 803 can then be provided to the content renderer 804 for presentation of content to a user. The decoder-in buffer 801 is empty. The second decoder-in buffer 1100 has still received two of the five sub-portions of the second-time-point delayed data portion at 1004.

FIG. 15 shows the situation later than the situation shown in FIG. 14. Part of the content of the decoded delayed data portion in the decoder-out buffer 803 has been provided to the content renderer 804. Accordingly, the content renderer 804 is shown with a number “1” to illustrate that one communication round of content has been provided thereto for presentation to the user. The decoder-out buffer 803 now has four communication rounds worth of content left to provide to the content renderer 804.

In this example, the controller 706 need not continue to request delayed data portions from locations subsequent to said data portion at the first time point, i.e. at location 1106, because there is sufficient decoded content in the decoder-out buffer 803 in terms of time, to enable the sub-portions of the second-time-point delayed data portion at 1004 to be fully retrieved, before the decoder-out buffer 803 is empty.

FIG. 16 shows the situation after one communication round following the situation shown in FIG. 15. Accordingly, the content renderer 804 has received a second portion of the content of the decoded delayed data portion from the decoder-out buffer 803 for rendering to a user. Accordingly, the content renderer 804 is shown with a number “2”. The decoder-out buffer 803 now has three remaining portions to provide the content renderer 712, as illustrated by the number “3”.

As mentioned previously, the decoder-in buffer 801 is no longer utilised and therefore it has been removed from this figure. The controller 706 now only provides for requesting of second-time-point delayed data portions at 1004. A third sub-portion from the delayed data portion at 1004 has been provided to the second decoder-in buffer 1100. Accordingly, the second decoder-in buffer 1100 is shown with a number “3” indicating it has received three sub-portions and the delayed data portion at 1004 is shown with a number “2” to illustrate that there are two sub-portions left to transfer.

FIG. 17 shows the situation after one communication round following the situation shown in FIG. 16. Accordingly, the content renderer 804 has received a third portion of the content of the decoded delayed data portion from the decoder-out buffer 803 for rendering to a user. Accordingly, the content renderer 804 is shown with a number “3”. The decoder-out buffer 803 now has two remaining portions to provide the content renderer 712, as illustrated by the number “2”.

A fourth sub-portion from the delayed data portion at 1004 has been provided to the second decoder-in buffer 1100. Accordingly, the second decoder-in buffer 1100 is shown with a number “4” indicating it has received four sub-portions and the delayed data portion at 1004 is shown with a number “1” to illustrate that there is one sub-portion left to transfer. Thus, one further communication round is required before the second decoder-in buffer 1100 receives the final sub-portion and accordingly contains a decodable delayed data portion.

FIG. 18 shows the situation after one communication round following the situation shown in FIG. 17. Accordingly, the content renderer 804 has received a fourth portion of the content of the decoded delayed data portion from the decoder-out buffer 803 for rendering to a user. Accordingly, the content renderer 804 is shown with a number “4”. The decoder-out buffer 803 now has one remaining portion to provide the content renderer 712, as illustrated by the number “1”.

A fifth sub-portion from the delayed data portion at 1004 has been provided to the second decoder-in buffer 1100. Accordingly, the second decoder-in buffer 1100 is shown with a number “5” indicating it has received all the sub-portions required to decode the second-time-point delayed data portion from location 1004. The delayed data portion at 1004 is shown without a number to illustrate that all the sub-portions have now been transferred to the reception device.

FIG. 19 shows the situation after one communication round following the situation shown in FIG. 18. Accordingly, the content renderer 804 has received a fifth portion of the content of the decoded delayed data portion from the decoder-out buffer 803 for rendering to a user. Accordingly, the content renderer 804 is shown with a number “5”. The decoder-out buffer 803 is now empty.

The second decoder-in buffer 1100 holds a decodable delayed data portion which, now that the decoder-out buffer 803 is empty can be decoded by the decoder processor 802. At this point the second-time-point delayed data portion from location 1004 is ready to be decoded and therefore the controller need not request the next delayed data portion at 1900.

FIG. 20 shows the situation later than that shown in FIG. 19 within the same communication round. Accordingly, the second-time-point delayed data portion has been decoded and it present in the decoder-out buffer 803 ready for presentation by the content renderer 712.

FIG. 21 shows the situation after one communication round following the situation shown in FIG. 20. Accordingly, the content renderer 712 has received a first portion of the content of the decoded delayed data portion from the decoder-out buffer 803 for rendering to a user, shown by number “1” in indicator 804. Thus, at this point, the reception device has switched from presenting content from the first time point to presenting content from the second time point. Accordingly, the controller has actioned the request to switch from decoding delayed data portions from a first time point to decoding delayed data portions from a different, second time point while avoiding periods where the content renderer 804 is unable to present content to the user.

It will be appreciated that the switch in time point may cause repetition in the content presented to a user but the actions of the controller 706 as described above have avoided a gap in the presentation of content.

Accordingly, the rendered content indicator 804 of the content renderer 712 is shown with a number “1”. The decoder-out buffer 803 has four remaining portions of decoded content to provide to the content renderer 804 and is shown with a number “4”.

The requesting of delayed data portion now proceeds from the position of the current read pointer 805. Accordingly, a first sub-potion of the delayed data portion 1900 directly subsequent to the second-time-point delayed data portion at 1004 is requested and retrieved from the host device. The second decoder-in buffer 1100 thus holds a first sub-portion shown by the number “1”. The reception device may now be considered to be in a steady state in which further delayed data portions may be retrieved as required. The controller 706 may await the receipt of a further request to switch from decoding delayed data portions from the current time point to decoding delayed data portions from a different time point.

FIG. 22 shows a flow chart illustrating an example method of the disclosure. The method comprises, at step 2201, receiving a request to switch from decoding delayed data portions from a first time point to decoding delayed data portions from a different, second time point, the request received while the controller is configured to receive the delayed data portion from said first time point for decoding. At step 2202, identifying one or more second-time-point delayed data portions to request from the host device based on the second time point and the indexing information. At step 2203, requesting the one or more identified second-time-point delayed data portions from the host device. At step 2204, while one or both of requesting and receiving the one or more second-time-point delayed data portions, requesting one or more delayed data portions corresponding to the first time or at least corresponding to a time subsequent thereto for decoding for at least some of a total transfer time for receiving the one or more second-time-point delayed data portions, the total transfer time comprising the sum of the predetermined transfer times for each sub-portion of the one or more identified second-time-point delayed data portions. 

The invention claimed is:
 1. A reception device comprising: at least one receiver and a corresponding delay buffer configured to receive portions of data for at least one data stream; the at least one delay buffer comprising at least part of a host device and configured to store the portions of data received by a respective receiver; and a memory configured to maintain indexing information for the or each of the delay buffers, the indexing information providing at least an indication of time points in the content of each of the portions of data; and a controller configured to request delayed data portions from one or more of the at least one delay buffer of the host device for decoding of the delayed data portions; the reception device configured such that each delayed data portion received by the reception device from the host device in response to each request of the controller is received as a plurality of consecutively received sub-portions, each sub-portion comprising a subset of the content of the delayed data portion, the receipt of each sub-portion taking at least a predetermined transfer time and each delayed data portion configured such that all of its constituent sub-portions are required for decoding said delayed data portion; wherein based on a request to switch from decoding delayed data portions from a first time point to decoding delayed data portions from a different, second time point, the request received while the controller is configured to receive the delayed data portion from said first time point for decoding; the controller is configured to perform the following; (a) identify one or more second-time-point delayed data portions to request from the host device based on the second time point and the indexing information; (b) request the one or more identified second-time-point delayed data portions from the host device; and (c) while one or both of requesting and receiving the one or more second-time-point delayed data portions, request one or more delayed data portions corresponding to the first time or at least corresponding to a time subsequent thereto for decoding for at least some of a total transfer time for receiving the one or more second-time-point delayed data portions, the total transfer time comprising the sum of the predetermined transfer times for each sub-portion of the one or more identified second-time-point delayed data portions.
 2. The reception device of claim 1 wherein the controller is configured to determine the total transfer time for receiving the one or more identified second-time-point delayed data portions using meta information indicative of the number of sub-portions required to receive the one or more identified delayed data portions, and based on the determined total transfer time, determine the one or more requests, required in step (b), of the one or more delayed data portions corresponding to the first time or times consecutively subsequent thereto in order to continue decoding said delayed data portions while the one or more identified second-time-point delayed data portions are received from the host device.
 3. The reception device of claim 1, wherein the controller is configured to determine the total transfer time for receiving the one or more identified second-time-point delayed data portions using meta information indicative of the number of sub-portions required to receive the one or more identified delayed data portions, and based on the determined total transfer time, a switch time comprising the time the controller provides for switching from decoding the delayed data portions associated with the first time to from decoding the second-time-point delayed data portions.
 4. The reception device of claim 1, wherein the content of the data portions comprises one or both of audio and video for presentation to a user when decoded and the continued decoding of the one or more delayed data portions requested during the one or both of requesting and receiving of the one or more identified second-time-point delayed data portions provides for gapless presentation of the audio or video to the user.
 5. The reception device of claim 1, wherein step (a) includes the identification of a first candidate delayed data portion comprising the delayed data portion directly subsequent to the delayed data portion containing the second time point, determination of the total transfer time of the first candidate delayed data portion and wherein: if the total transfer time of the first candidate delayed data portion is less than the time between the second time point and a time point defined by the start of the content of the first candidate delayed data portion, the controller is caused to identify said first candidate delayed data portion as the second-time-point delayed data portion; and if the total transfer time of the first candidate delayed data portion is greater than the time between the second time point and the time point defined by the start of the content of the first candidate delayed data portion, the controller is caused to identify a delayed data portion received subsequent to the first candidate delayed data portion as the second-time-point delayed data portion.
 6. The reception device of claim 1, wherein the reception device includes a first buffer and a second buffer for receiving delayed data portions from the host device; the first buffer configured to receive the one or more delayed data portions corresponding to the first time or at least corresponding to a time subsequent thereto; and the second buffer configured to receive the one or more identified second-time-point delayed data portions; the controller configured to provide the one or more delayed data portions of the first buffer to a decoder while the second buffer receives at least all of the sub-portions of one of the one or more of the identified second-time-point delayed data portions.
 7. The reception device of claim 1, wherein the reception device includes a decoder configured to decode the delayed data portions received from the host device, the decoder configured to provide decoded delayed data portions for presentation to a user.
 8. The reception device of claim 7, wherein the reception device includes a decoder-out buffer configured to hold decoded delayed data portions for presentation to a user by a content renderer.
 9. The reception device of claim 8, wherein the reception device includes a content renderer configured to receive a decoded data stream formed of the decoded delayed data portions held in said decoder-out buffer for presentation to a user.
 10. The reception device of claim 1, wherein each request by the controller for delayed data portions from the host device comprise a request for delayed data portions from all of the delay buffers.
 11. The reception device of claim 1 wherein the indexing information comprises read and write pointers for each delay buffer.
 12. The reception device of claim 1, wherein the at least one receiver is configured to receive a data stream selected from a frequency modulated FM stream, a Digital Audio Broadcast DAB stream, a Digital Audio Broadcast DAB+ stream, a T-DMB stream, an analogue audio or video stream and a digital audio or video stream.
 13. A method for a reception device comprising at least one receiver and a corresponding delay buffer configured to receive portions of data for at least one data stream; the delay buffers comprising at least part of a host device and configured to store the portions of data received by a respective receiver; and a memory configured to maintain indexing information for the or each of the delay buffers, the indexing information providing at least an indication of time points in the content of each of the portions of data; and a controller configured to request delayed data portions from one or more of the at least one delay buffer of the host device for decoding of the delayed data portions; the reception device configured such that each delayed data portion received by the reception device from the host device in response to each request of the controller is received as a plurality of consecutively received sub-portions, each sub-portion comprising a subset of the content of the delayed data portion, the receipt of each sub-portion taking at least a predetermined transfer time and each delayed data portion configured such that all of its constituent sub-portions are required for decoding said delayed data portion; wherein based on a request to switch from decoding delayed data portions from a first time point to decoding delayed data portions from a different, second time point, the request received while the controller is configured to receive the delayed data portion from said first time point for decoding; the controller is configured to perform the method of; (a) identifying one or more second-time-point delayed data portions to request from the host device based on the second time point and the indexing information; (b) requesting the one or more identified second-time-point delayed data portions from the host device; and (c) while one or both of requesting and receiving the one or more second-time-point delayed data portions, requesting one or more delayed data portions corresponding to the first time or at least corresponding to a time subsequent thereto for decoding for at least some of a total transfer time for receiving the one or more second-time-point delayed data portions, the total transfer time comprising the sum of the predetermined transfer times for each sub-portion of the one or more identified second-time-point delayed data portions.
 14. A presentation device for presentation of one or more of video and audio content to a user, the presentation device comprising the reception device of claim 1 and a host device for buffering data streams received by the reception device.
 15. A host device for buffering data streams for a multi-source receiver comprising: an input configured to receive portions of data from a reception device in a forwarding message, the portions of data forming part of at least one data stream, the input further configured to receive indexing information associated with at least one delay buffer in the forwarding message; at least one delay buffer configured to store the respective portions of data in the at least one delay buffer in dependence on the indexing information; the host device configured such that each delayed data portion transferred to the reception device from the host device in response to each request of a controller of the reception device is transferred as a plurality of consecutively transferred sub-portions, each sub-portion comprising a subset of the content of the delayed data portion, the transfer of each sub-portion taking at least a predetermined transfer time and each delayed data portion configured such that all of its constituent sub-portions are required for decoding said delayed data portion at the reception device; and while transferring the sub-portions of one or more second-time-point delayed data portions to the reception device, transferring one or more delayed data portions corresponding to a first, different time or at least corresponding to a time subsequent thereto for decoding by the reception device for at least some of a total transfer time for transferring the one or more second-time-point delayed data portions, the total transfer time comprising the sum of the predetermined transfer times for each sub-portion of the one or more identified second-time-point delayed data portions.
 16. The method of claim 13, wherein the controller is configured to determine the total transfer time for receiving the one or more identified second-time-point delayed data portions using meta information indicative of the number of sub-portions required to receive the one or more identified delayed data portions, and based on the determined total transfer time, determine the one or more requests, required in step (b), of the one or more delayed data portions corresponding to the first time or times consecutively subsequent thereto in order to continue decoding said delayed data portions while the one or more identified second-time-point delayed data portions are received from the host device.
 17. The method of claim 13, wherein the controller is configured to determine the total transfer time for receiving the one or more identified second-time-point delayed data portions using meta information indicative of the number of sub-portions required to receive the one or more identified delayed data portions, and based on the determined total transfer time, a switch time comprising the time the controller provides for switching from decoding the delayed data portions associated with the first time to from decoding the second-time-point delayed data portions.
 18. The method of claim 13, wherein the content of the data portions comprises one or both of audio and video for presentation to a user when decoded and the continued decoding of the one or more delayed data portions requested during the one or both of requesting and receiving of the one or more identified second-time-point delayed data portions provides for gapless presentation of the audio or video to the user.
 19. The method of claim 13, wherein step (a) includes identifying a first candidate delayed data portion comprising the delayed data portion directly subsequent to the delayed data portion containing the second time point, determination of the total transfer time of the first candidate delayed data portion and wherein: if the total transfer time of the first candidate delayed data portion is less than the time between the second time point and a time point defined by the start of the content of the first candidate delayed data portion, the controller is caused to identify said first candidate delayed data portion as the second-time-point delayed data portion; and if the total transfer time of the first candidate delayed data portion is greater than the time between the second time point and the time point defined by the start of the content of the first candidate delayed data portion, the controller is caused to identify a delayed data portion received subsequent to the first candidate delayed data portion as the second-time-point delayed data portion.
 20. The method of claim 13, wherein each request by the controller for delayed data portions from the host device comprise a request for delayed data portions from all of the delay buffers. 